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SubjectRe: [f2fs-dev] [PATCH] f2fs: initialize page->private when using for our internal use
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On 2021/7/5 13:22, Jaegeuk Kim wrote:
> We need to guarantee it's initially zero. Otherwise, it'll hurt entire flag
> operations.

Oops, I didn't get the point, shouldn't .private be zero after page was
just allocated by filesystem? What's the case we will encounter stall
private data left in page?

Cc Matthew Wilcox.

Thanks,

>
> Fixes: b763f3bedc2d ("f2fs: restructure f2fs page.private layout")
> Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
> ---
> fs/f2fs/data.c | 2 ++
> fs/f2fs/f2fs.h | 5 ++++-
> 2 files changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> index 3a01a1b50104..d2cf48c5a2e4 100644
> --- a/fs/f2fs/data.c
> +++ b/fs/f2fs/data.c
> @@ -3819,6 +3819,8 @@ int f2fs_migrate_page(struct address_space *mapping,
> get_page(newpage);
> }
>
> + /* guarantee to start from no stale private field */
> + set_page_private(newpage, 0);
> if (PagePrivate(page)) {
> set_page_private(newpage, page_private(page));
> SetPagePrivate(newpage);
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index 65befc68d88e..ee8eb33e2c25 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -1331,7 +1331,8 @@ enum {
> #define PAGE_PRIVATE_GET_FUNC(name, flagname) \
> static inline bool page_private_##name(struct page *page) \
> { \
> - return test_bit(PAGE_PRIVATE_NOT_POINTER, &page_private(page)) && \
> + return PagePrivate(page) && \
> + test_bit(PAGE_PRIVATE_NOT_POINTER, &page_private(page)) && \
> test_bit(PAGE_PRIVATE_##flagname, &page_private(page)); \
> }
>
> @@ -1341,6 +1342,7 @@ static inline void set_page_private_##name(struct page *page) \
> if (!PagePrivate(page)) { \
> get_page(page); \
> SetPagePrivate(page); \
> + set_page_private(page, 0); \
> } \
> set_bit(PAGE_PRIVATE_NOT_POINTER, &page_private(page)); \
> set_bit(PAGE_PRIVATE_##flagname, &page_private(page)); \
> @@ -1392,6 +1394,7 @@ static inline void set_page_private_data(struct page *page, unsigned long data)
> if (!PagePrivate(page)) {
> get_page(page);
> SetPagePrivate(page);
> + set_page_private(page, 0);
> }
> set_bit(PAGE_PRIVATE_NOT_POINTER, &page_private(page));
> page_private(page) |= data << PAGE_PRIVATE_MAX;
>

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